From DE 41 21 055 A1, a circuit arrangement is known for limiting the switching-on current of incandescent bulbs. The circuit arrangement includes a protective resistor connected in series to an incandescent bulb. Parallel to the protective resistor, a switching transistor, which is controlled by an ignition transistor, is provided. The ignition transistor is fed on the input side with the voltage drop which occurs on the incandescent bulb. After the supply voltage is switched on, the voltage drop on the incandescent bulb gradually increases, because the resistance of the incandescent bulb increases as the operating temperature increases. When a specified voltage drop on the incandescent bulb is reached, the ignition transistor switches through, and controls the switching transistor in such a way that it also switches through, and thus bridges the protective resistor, so that the current through the incandescent bulb is no longer limited by the protective resistor.
With this circuit arrangement according to the prior art, the effect of the current limitation is heavily dependent on the type of load and the value of the supply voltage, so that the circuit arrangement must be newly dimensioned for each load and each supply voltage. Additionally, at the instant when the switching and ignition transistors are switched through, high switching current peaks can occur briefly. These can load the supply voltage source as well as cause damage to the load. Also, with this circuit arrangement, even after the switching transistor is switched through, a finite voltage drop occurs between the collector and emitter of the switching transistor, and/or at the protective resistor, resulting in production of dissipated heat.